Fabrication of SAW resonators on single-crystal diamonds using Minimal-Fab process

摘要

Diamond is known to have the highest sound velocity of all materials, and therefore, has been applied to high frequency surface acoustic wave (SAW) devices in the gigahertz range. Our earlier research has shown much potential for diamond SAW resonators and filters on single crystal substrates at frequencies above 3 GHz. However, single crystal diamond wafers of only up to two-inch in diameter have been realized; in consequence, diamond SAW resonators were far from commercial development. A novel CMOS device fabrication system developed by Hara et al., called the Minimal-Fab process, was thus applied in the fabrication of SAW resonators. It utilizes a half-inch diameter wafer, and proceeds with device fabrication via half-micron fine pattern lithography, without needing a cleanroom. Here, we discuss the potential of the Minimal-Fab process, and our fabrication of diamond SAW resonators using it, where we used a half-inch diamond wafer and a small substrate of 4×4 mm² size.